The long term goals are to use the tools of molecular biology to study a series of problems in evolution, in the specificity of the nervous system, and in early development. The exon structure of known genes will be analyzed in order to understand protein structure in terms of a simple set of primordial components that were used to assemble proteins. The alternative splicing of small exons in the immunoglobulin-like domains of the neural cell adhesion molecule, N-CAM, will be studied to determine if these alternative splices produce minor isotypes of novel specificities in rare cells, and if these specificities have to do with the patterning of the brain or the organism. The phylogeny of RNA editing will be studied to determine the origin of this novel biological process.